First-principles study of structure, electronic, and magnetic properties of C sites vacancy defects in water adsorbed graphene/MoS van der Waals heterostructures.

We have studied structure, electronic, and magnetic properties of water adsorbed vdW heterostructure graphene/MoS (w-(HS)G/MoS) and its C sites vacancy defects materials (w-C-(HS)G/MoS) by using a spin polarized density functional theory (DFT) method of calculations within DFT-D2 approach to take in to account of vdW interactions. All the structures are optimized and relaxed by BFGS method using computational tool Quantum ESPRESSO package. By structural analysis, we found that both w-(HS)G/MoS and w-C-(HS)G/MoS are stable materials. The stability and compactness of these materials decrease with an increase in their defects concentrations. From band structure calculations, our findings show that w-(HS)G/MoS has a metallic nature, and there is formation of n-type Schottky contact of barrier height 0.42 eV. Also, the left 1C atom vacancy defects in w-(HS)G/MoS (L1C-w-(HS)G/MoS) and center 1C atom vacancy defects in w-(HS)G/MoS (C1C-w-(HS)G/MoS) materials have no band gap for up and down spin electronic states, indicating that they have also a metallic nature. On the other hand, 2C atom vacancy defects in w-(HS)G/MoS (2C-w-(HS)G/MoS) has a small band gap for up spins states and no band gap for down spin electronic states which means that the band structure resembles with half metallic nature. Thus, the endowment of metallic nature decreased with increase in the concentrations of defects in structures. To study the magnetic properties in materials, DOS and PDOS calculations are used, and we found that non-magnetic w-(HS)G/MoS material changes to magnetic in all the three different L1C-w-(HS)G/MoS, C1C-w-(HS)G/MoS, and 2C-w-(HS)G/MoS materials with vacancy. L1C-w-(HS)G/MoS, C1C-w-(HS)G/MoS, and 2C-w-(HS)G/MoS have magnetic moments of + 0.21 μ/cell, + 0.26 μ/cell, and - 2.00 μ/cell, respectively. The spins of electrons in 2s and 2p orbitals of C atoms give a principal effect of magnetism in w-C-(HS)G/MoS materials.